Device for controlling the pressure in a vehicle tyre
A device ( 10 ) is disclosed for providing air to a tire which is mounted on a wheel rim which itself is free to rotate about a fixed, that is, non-rotatable axle 22 . The device includes a pump ( 50, 52, 54, 62 ) which in use rotates with the tire and which is configured to provide, when activated, air under pressure to the tire. There is a pump drive system for activating the pump. The pump drive system comprising a piston rod ( 56 ) which is connected to and rotates with the tire and a body ( 40 ) which rotates in unison with the rod ( 56 ) while the pump is inactive. An electric motor ( 68 ) rotates the body ( 40 ) with respect to the rod ( 56 ) to activate the pump and provide air to the tire. Rotation of the body ( 40 ) is superimposed on rotation of the pump with the tire. The device also includes a stator component ( 26 ) and coils ( 30 ) and magnets ( 32 ) for generating, by electrical induction, power for driving the motor using the relative rotation between the second part and the stator component ( 26 ).
1. A device for providing air to a tyre which is mounted on a wheel rim which is free to rotate about a non-rotatable axle, the device comprising:—
a) a pump which in use rotates with the tyre and which is configured to provide, when activated, air under pressure to the tyre;
b) a pump drive system for activating the pump, the pump drive system comprising a first part which is connected to and rotates with the tyre and a second part which rotates in unison with the first part whilst the pump is inactive;
c) an electric motor for rotating said second part with respect to the first part to activate the pump and provide air to the tyre;
d) a stator component; and
a plurality of alternator magnets and a plurality of coils for generating, by electrical induction, power for driving said motor, the power is generated by a relative rotation between the plurality of alternator magnets and the plurality of coils;
wherein the plurality of alternator magnets or the plurality of coils rotate with said first part and the other of the plurality of alternator magnets and the plurality of coils are carried by the stator component.
2. The device as claimed in claim 1 , wherein said stator component is configured to be attached to said fixed axle and the second part includes a component which rotates with the tyre.
3. The device as claimed in claim 2 , wherein a first of said components carries the plurality of magnets, and a second of the components carries the plurality of coils;
wherein the plurality of magnets are arranged in a first circular array and the plurality of coils are arranged in a second circular array;
wherein the diameter of the first and second circular arrays is the same.
4. The device as claimed in claim 3 , further comprising a battery pack for storing power generated by inductive interaction between the coils and the magnets.
5. The device as claimed in claim 4 , further comprising:
a drive pulley fixed to an output shaft of the motor,
a driven pulley fixed to said second part and rotates therewith, and
a drive element entrained around said pulleys for rotating said driven pulley and said second part relative to the first part when the motor is activated.
6. The device as claimed in claim 2 , further comprising:
a drive pulley fixed to an output shaft of the motor,
a driven pulley fixed to said second part and rotates therewith, and
a drive element entrained around said pulleys for rotating said driven pulley and said second part relative to the first part when the motor is activated.
7. The device as claimed in claim 3 , further comprising:
a drive pulley fixed to an output shaft of the motor,
a driven pulley fixed to said second part and rotates therewith, and
a drive element entrained around said pulleys for rotating said driven pulley and said second part relative to the first part when the motor is activated.
8. The device as claimed in claim 1 , further comprising:
a drive pulley fixed to an output shaft of the motor,
a driven pulley fixed to said second part and rotates therewith, and
a drive element entrained around said pulleys for rotating said driven pulley and said second part relative to the first part when the motor is activated.